Highly sensitive and selective detection of benzene, toluene, xylene, and formaldehyde using Au-coated SnO₂ nanorod arrays for indoor air quality monitoring

We report the high performance of Au-coated SnO2 nanorod gas sensors for the detection of hazardous indoor volatile organic compounds (VOCs), such as benzene, toluene, xylene, and formaldehyde (BTXF) gases. Densely ordered SnO2 nanorod arrays were prepared via glancing angle deposition with an electron beam evaporator. The Au layer coating was used as a heterogeneous catalyst to promote the oxidation of VOCs, such as hydrocarbons. After optimizing the Au thickness, the sensor exhibited an excellent sensing response and a rapid response time of < 2.5 s for 10 ppm of BTXF gases. The maximum response was similar to 662 for formaldehyde at 400 degrees C, similar to 328 for toluene at 450 degrees C, similar to 170 for xylene at 400 degrees C, and similar to 139 for benzene at 500 degrees C, which are significantly higher than those of previously reported metal-oxide-semiconductor-based sensors. Each gas was selectively detected by integrating the sensor into a miniaturized gas chromatography (GC) system. The sensors detected ppb-level gas concentrations. Significantly, GC analysis revealed that four types of gases could be separately detected in a mixed gas within 5 min. Our study shows that Au-coated SnO2 nanorod gas sensors integrated with GC can be used as a facile indoor pollutant monitoring system.